1. Field of the Invention
The invention relates to an apparatus for distributing fiber optic signals from a provider to a plurality of subscribers or end users.
2. Background
Since the end of the 20th century, passive optical network (PON) architecture has gained worldwide acceptance and now underlies much of the growth of the telecommunications industry. Today, however, PON architecture is undergoing a technological transformation that is driving it into the next generation.
PON is a point-to-multipoint architecture that is used to deliver fiber to the premises by distributing signals through unpowered optical splitters to a multitude of subscribers. On one end of the network, in the central office, an optical line terminal converts and packages electrical signals into an optical output. These signals are distributed over the optical network via a backbone cable, which links between the inside-plant and outside-plant environments. The packaged signal is distributed further into the network by means of an optical splitter, which divides the signal among several fibers, each of which goes to a different subscriber.
At the other end of the network, at the subscriber's premises, an optical network terminal or optical network unit provides a termination and separation point for the delivered optical signal. This piece of hardware converts the optical signal into electrically formatted subcomponents for delivery of telephone, television, and Internet service to end-user devices.
Most PON architectures are centered on distribution cabinets that house unpowered optical splitters and tie together the network. These cabinets are large, expensive and cumbersome, and usually require below-grade handholes for splicing fiber. Installing them requires, at a minimum, expensive excavation equipment and labor, and may also require obtaining permits for placement. Including labor and materials costs (cabinet, splitters, pigtails and so forth), the cost can easily exceed $15,000 for a fully loaded 288-fiber setup. Planning for the assembly and implementation of a distribution cabinet can also be a daunting task. Typically this installation requires several days of labor commitment as well as multiple installers.
From a business development and network design approach, placing the distribution cabinet requires mapping out a group of subscribers and ascertaining likely take rates. Because the fiber infrastructure is defined up front but the active customers are not known until services are marketed, there is a large amount of pressure on the provider to maximize capacity—which tends to increase the cost per customer.
This topology—a centralized distribution point in the middle of a fiber web—limits the flexibility of a traditional PON architecture. Not only does the distribution point require a large investment, but also its reach defines and limits the network's area of coverage.
Rural applications are not efficiently covered by this architecture; their lower subscriber densities require more fiber to cover a smaller customer base, which in turn significantly increases infrastructure costs. In urban layouts, the central distribution architecture is limited by its inability to effectively serve high-density regions. The typical 1×16 and 1×32 splitters with which central distribution cabinets are outfitted do not provide enough flexibility for a high-rise building that may contain hundreds of potential customers. Even in suburban housing developments, traditional PON architectures do not accommodate widely varied take rates in a cost-effective manner. In recent years, deployers have begun to demand ways to accommodate smaller housing developments without the large upfront financial commitment of a traditional distribution cabinet.
The project commitment associated with distribution cabinet deployment is burdensome to the overall design and construction of a PON, placing an unbalanced focus on penetration rates and break-even points in the life cycle and diverting attention from network setup. Fortunately, because of the push to cut installation costs and increase flexibility, new solutions have begun to emerge as alternatives to distribution cabinet deployment.
Current technology for distributing cable, Internet, data, etc., to subscribers/homes uses fiber distribution hubs (FDHs). An example of and FDH is disclosed in U.S. Pat. No. 7,200,317—Systems and Methods for Optical Fiber Distribution and Management. FDHs typically consist of a passive optical network (PON) cabinet located in an outside plant (OSP) or multiple dwelling unit (MDU) environment. The cabinet is usually a ruggedized metal cabinet with a product life of twenty years. The FDH also allows for passive upgrading of splitter modules and distribution of splitter module output fibers.
Examples of related technology includes the splitters disclosed in U.S. Pat. No. 7,218,828—Optical Fiber Power Splitter Module Apparatus and U.S. Pat. No. 7,515,805—Fiber Optic Splitter. The '828 patent is directed to and discloses a multi-fiber push on (MPO) based splitter module. The objective of the '828 patent was to eliminate all of the fiber pigtails emanating from the splitter housing that were conventional at the time, such as disclosed in the '828 patent. It did this by using connectors/adapters for the input fibers and all of the output fibers. However, a disadvantage of this solution is that is does not allow the flexibility to have the input fiber spliced directly to the splitter. Spliced connections provide a connection and have lower loss than connectorized connections.
Therefore, there is a need for an architecture that allows more flexible layouts, where distribution points can be placed anywhere in the network. Outside-plant designers can now distribute signals at a wider variety of locations between the central office and fiber network endpoints.